The present invention relates to a dielectric duplexer having a plurality of resonators arranged in a row for use in mobile communication devices such as car phones and cellular phones.
Various prior art dielectric duplexer devices are configured in the form of a plurality of resonators arranged in a row in a dielectric ceramic porcelain block material such as porcelain. Each of the resonators is formed by coating the internal circumferential surface of a through-hole formed in the dielectric porcelain block with an internal conductor. A predetermined external circumferential surface of the dielectric porcelain block is coated with an external conductor. The resonators comprise two groups. One group serves as a transmission section, which is coupled with an input terminal pad formed on the predetermined external circumferential surface, separated from the external conductor. The other group serves as a reception section, which is coupled with an output terminal pad formed on the predetermined external circumferential surface, separated from the external conductor. An antenna terminal pad is formed on a mounting surface of the dielectric duplexer, separated from the external conductor in such a manner as to be coupled with the respective resonators of the transmission section and of the reception section located closest to one another in the row.
A further prior art dielectric duplexer device is configured as above but also includes an output terminal pad formed on a side surface of the dielectric porcelain block in order to face the resonators of the reception section in the vicinity of their open ends, whereby the output terminal pad is capacitively coupled with the resonators.
The above-mentioned dielectric duplexer device, i.e., the device with the output terminal pad formed on the side surface of the dielectric porcelain block while being capacitively coupled with the resonators of the reception section, involves the following problem. The dielectric duplexer is mounted on a printed circuit board such that the output terminal pad is electrically joined to a predetermined conductive path on the board through soldering. Since the state of a joint between the conductive path and the output terminal pad cannot be visually observed from the outside, the joint involves uncertainty as to electrical and mechanical connection and thus always falls under suspicion when a defect arises at a later stage. Further, since the connected state is invisible, the retention strength cannot be reliably known. Therefore, a dielectric duplexer of conventional configuration fails to provide sufficient electrical and mechanical reliability in a mounted state.
The present invention concerns a dielectric duplexer which has improved electrical and mechanical reliability in a mounted state and which facilitates adjustment of the coupling capacitance provided.
The present invention concerns a dielectric duplexer configured such that a plurality of resonators are arranged in a row in a dielectric material such as porcelain block. Each of the resonators are formed through coating an internal circumferential surface of a through-hole formed in the dielectric block with an internal conductor. A predetermined external circumferential surface of the dielectric porcelain block is coated with an external conductor. The resonators are divided into two groups. One group serves as a transmission section, which is coupled with an input terminal pad formed on the predetermined external circumferential surface, separated from the external conductor. The other group serves as a reception section, which is coupled with an output terminal pad formed on the predetermined external circumferential surface, separated from the external conductor. An antenna terminal pad is formed on a mounting surface of the dielectric duplexer separated from the external conductor in such a manner as to be coupled with the innermost resonator of the transmission section and the innermost resonator of the reception section.
In accordance with an important feature of the invention, the dielectric duplexer includes the output terminal pad formed on a side surface of the dielectric block and separated from the external conductor in such a manner as to face the vicinity of an open end of a resonator of the reception section. In addition, an extension electrode extends from the output terminal pad onto an end face of the dielectric block such that the extension electrode approaches the open end in order to capacitively couple with the resonator.
Since the extension electrode extending from the output terminal pad and located on the open end face is disposed to face the resonators of the reception section, a capacitance is provided between the extension electrode and the internal conductor of the resonator. This capacitance can be readily corrected or adjusted by adjusting the position of the end of the extension electrode. The end position is adjusted by, for example, cutting off a portion of the end or adding a conductor to the end.
When the dielectric duplexer is mounted on a printed circuit board such that the output terminal pad is electrically joined to a predetermined conductive path on the board through soldering, the extension electrode located on an exposed surface of the dielectric duplexer can be soldered to the predetermined conductive path from the outside. Thus, the output terminal pad is soldered at the bottom and side surfaces thereof, i.e., the output terminal pad is fillet-soldered. Therefore, the connection between the output terminal pad and the predetermined conductive path can be checked externally. Further, since the extension electrode is connected to the predetermined conductive path, the surface of joint is expanded, thereby enhancing the retention strength thereof.
Further features and advantages of the present invention will be set forth in, or apparent from, the detailed description of preferred embodiments thereof which follows.